A modal test of the John Paul Jones (DDG-53) mainmast structure and ma
st-mounted antennas was conducted. The test was part of a larger effor
t to accurately determine dynamic characteristics of the ''as-built''
mast/antenna system and survivability in the vibration and underwater
explosion (UNDEX) shock environment. Previous mathematical analysis of
the DDG-51 class mast and antennas predicted response acceleration le
vels during a shock trials scenario to be excessive in some areas. The
modal test results now provide, however, confirmed dynamic response c
haracteristics including mode shapes, frequencies, and damping for the
structure. The test data accounts for the flexibility of ship's struc
ture including the deckhouse supporting the mast. In addition, the nat
ural frequencies of the antennas were determined for the response rang
e of the mast structure with the flexibility of the supporting foundat
ions taken into account. Using the test results, a finite element mode
l of the mast structure and antennas was built accurately representing
the dynamic characteristics of the system. Dynamic transient shock an
alysis was conducted to provide response predictions of the mast and a
ntennas using the validated model. Any potential response amplificatio
n conditions that might result in failure during shock trials were ide
ntified.